Many water supply systems include a water storage tank, such as an elevated water tower or an on-ground water tank. A water storage tank may operate in conjunction with underground or surface service reservoirs and may store treated water close to where the water will be used. Many water storage tanks provide distribution of potable water as well as emergency storage for fire protection or for during power outages. Water storage tanks also often serve as a reservoir to help meet water needs during peak usage times. In particular, the water level in the tank may fall during certain peak usage hours of the day, and the tank may subsequently be refilled during non-peak usage hours. Accordingly, a water supply in the tank may constantly be, at least partially, drained and refilled.
Water storage tanks are often quite large and may hold on the order of 100,000 gallons and up to 2 million gallons or more. Often, a small amount of sediment or particulate in the treated water will collect at the bottom of the tank. Over time, this may accumulate to a large amount. This accumulation is a potentially serious issue, especially for potable water. It may be desirable to mix water at the bottom of the tank with water at the top of the tank so as to reduce settlement and thereby prevent sludge accumulation in the bottom of the tank. Known water mixing systems may use moving agitators or may passively circulate water using energy created during the fill and draw cycles. These systems are of limited effectiveness and/or have other disadvantages. Additionally, all or most components of known systems are provided in an interior section of the tank, making maintenance and repair more costly and time-consuming.